The present invention relates generally to an apparatus and method for manufacturing reconstituted tobacco sheet and more particularly to an apparatus and method in which reconstituted tobacco sheet is produced by applying a tobacco containing slurry to a heated cylindrical dryer.
During the production and processing of tobacco products, including aging, blending, sheet forming, cutting, drying, cooling, screening, shaping and packaging, considerable amounts of tobacco fines, dust, stems and other small tobacco plant parts are generated. It is known that such small tobacco plant parts can be combined with a binder material to form a coherent sheet, which resembles leaf tobacco and which is commonly referred to as reconstituted tobacco.
It is also known to produce such reconstituted tobacco sheet by a variety of processes. A commonly used process is known as a band process, which is described in U.S. Pat. No. 4,497,331. Such a process typically involves applying a slurry of tobacco particles plus other additives and adhesives by some means, such as a reverse roll coater, to a continuous carrier belt where the slurry is partially dried (typically to a moisture content of about 40%). Then, after the sheet is removed from the belt it is dried further to an acceptable moisture level, typically about 16%.
Another known process uses a paper making machine in which water is drained from a fibrous slurry of tobacco particles, and sheet that is formed is subsequently treated and dried. Such paper making machines are described in U.S. Pat. No. 4,497,331 and in United Kingdom patent No. 1,171,878.
The band process and apparatus possesses a number of known disadvantages. One such disadvantage is that the carrier belt typically is over 100 feet in length, and may be as long as 400 feet. Accordingly, there is need in the art for an apparatus and method for making a reconstituted tobacco sheet that uses a smaller and more economical apparatus.
Another disadvantage is that ammonia typically is added to the tobacco containing slurry in order to break down pectin in order to speed the formation of a coherent sheet. As a consequence, tobacco shreds cut from such ammonia containing sheet generally are not used in menthol cigarettes because ammonia reacts with menthol to cause an undesirable taste. Accordingly, there is a need in the art for an apparatus and method for making reconstituted tobacco sheet that does not require the use of ammonia.
A further disadvantage is low tensile strength of the reconstituted tobacco sheet, which causes increased generation of tobacco fines from cutting operations. In known processes, tensile strength is reduced because high temperatures are required to produce adequate drying during high speed operation.